1. Field of the Invention
This invention relates to a method of improving the storage properties of a color photographic material and also to a color photographic material having improved storage properties, in particular to a silver halide color photographic material having a silver halide emulsion layer containing a magenta dye forming coupler or a magenta forming coupler capable of forming a magenta dye image having excellent hue and fastness.
2. Description of the Prior Art
In the field of silver halide color photography, a magenta dye forming coupler used for forming magenta dye images must meet various conditions. That is to say, it is required that the magenta dye forming coupler shows a high coupling activity in the coupling reaction with the oxidation product of a color developing agent, the coupler can form, by color development, a magenta dye image having suitable spectral characteristics for the color reproduction by the subtractive color process (since a magenta dye image absorbs the light in the wave length region to which the human eye is most sensitive, the spectral characteristics of the magenta dye image are a very important factor dominating the color reproducibility in color photography), and the magenta dye forming coupler can form a magenta dye image having high fastness to light, heat, moisture, etc.
Also, when the magenta dye forming coupler is of the type which is incorporated in a silver halide emulsion layer of a color photographic material, it is further required that the properties, in particular, the coupling activity of the coupler is not reduced during the storage of the color photographic material, the coupler can be easily introduced in the silver halide emulsion, the coupler incorporated in the silver halide emulsion layer is stable without concerns on crystallization, etc., during the storage of the photographic material, and further the coupler does not provide, after color development, the causes of color staining by the actions of light, heat, moisture, etc., be present.
As magenta dye forming couplers, various compounds such as pyrazolone couplers, cyanoacetyl couplers, indazolone couplers, etc., are known. In particular, as the pyrazolone type magenta forming couplers, there are proposed, for instance, the 3-anilino-5-pyrazolones (see, e.g., U.S. Pat. No. 2,311,081, etc.), the 3-alkoxy-5-pyrazolone couplers (see, e.g., U.S. Pat. No. 2,439,098, etc.), the 3-acylamino-5-pyrazolones (see, e.g., U.S. Pat. Nos. 2,369,489; 2,600,788, etc.), and the 3-ureido-5-pyrazolones (see e.g., U.S. Pat. No. 3,558,319, etc.). Of these pyrazolone couplers, the 3-anilino-5-pyrazolone couplers are excellent in providing dye images which have high fastness to heat and moisture. Non-diffusible magenta couplers which belong to the 3-anilino-5-pyrazolone couplers and have a ballast group in the molecule so that they can be introduced in silver halide emulsion layers of photographic materials are described in U.S. Pat. Nos. 3,419,391; 3,519,429; 3,127,269; 3,684,514; 3,761,274 and 3,658,544; and U.S. Pat. application Ser. Nos. 415,864, filed Nov. 13, 1973; 415,853, filed Nov. 14, 1973 and 445,032 filed Feb. 22, 1974.
Of these 3-anilino-5-pyrazolone couplers, a coupler having a halogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a N-substituted amino group, an amido group, a hydroxyl group, a cyano group, or a nitro group at least one of the 2-position and the 6-position of the anilino group thereof and also a hydrophobic ballast group at the aromatic nucleus of the anilino group is particularly preferable in that the coupler has less undesired absorptions in the blue region and the red region, the coupler forms a magenta dye image having excellent spectral characteristics, and also the coupler has a high coupling activity.
The 3-substituted anilino-5-pyrazolone couplers as indicated above meet the various requirements as desirable magenta dye forming couplers but have a serious disadvantage in that the magenta dye images formed from such magenta couplers are insufficiently fast to right. Thus, various proposals have been made for minimizing this disadvantage to prevent the fading of the magenta dye images by light. According to a very effective method of these proposals, a phenolic compound is used together with the aforesaid magenta dye forming coupler. Preferred examples of such a phenolic compound are the alkoxyphenols, aryloxyphenols, hydroxycoumarans, hydroxychromans, and dihydroxyspirochromans as described in U.S. Pat. Nos. 3,432,300; 3,573,050; 3,574,627 and 3,764,337 and German Offenlegungsschriften 2,146,668.
However, when a photographic material containing the phenolic compound and the 3-substituted anilino-5-pyrazolone type magenta coupler as described above in a silver halide emulsion layer thereof is stored at an ordinary room temperature, the coupling density of the magenta coupler begins to reduce after about one month and the coupling density becomes less than a half of the value immediately after the production of the photographic material after about six months of storage. This phenomenon greatly reduces the commercial value of color photographic materials. Therefore, a means of removing those defficiencies has been desired.